Arsenic
Arsenic is the chemical element that has the symbol As and atomic number 33. Arsenic was first documented by Albertus Magnus in 1250. Its atomic mass is 74.92. This is a notoriously poisonous metalloid that has many allotropic forms: yellow (molecular non-metallic) and several black and grey forms (metalloids) are a few that are seen. Three metalloidal forms of arsenic with different crystal structures are found free in nature (the minerals arsenic sensu stricto and the much rarer arsenolamprite and pararsenolamprite), but it is more commonly found as arsenide and arsenate compounds. Several hundred such mineral species are known. Arsenic and its compounds are used as pesticides, herbicides, insecticides and various alloys. The most common oxidation states for arsenic are -3 (arsenides: usually alloy-like intermetallic compounds), +3 (arsenates(III) or arsenites, and most organoarsenic compounds), and +5 (arsenates: the most stable inorganic arsenic oxycompounds). Arsenic also bonds readily to itself, forming square As43- ions in the arsenide skutterudite. In the +3 oxidation state, the stereochemistry of arsenic is affected by possession of a lone pair of electrons. Chartetristics The word arsenic is borrowed from the Persian word Zarnikh meaning "yellow orpiment". Zarnikh was borrowed by Greek as arsenikon. Also from the similar Greek word "arsenikos" which means masculine or potent. Arsenic compounds (orpiment, realgar) have been known and used since ancient times. As the symptoms of arsenic poisoning were somewhat ill-defined, it was frequently used for murder until the advent of the Marsh test, a sensitive chemical test for its presence. (Another less sensitive but more general test is the Reinsch test.) Due to its use by the ruling class to murder one another and its potency and discreetness, arsenic has been called the Poison of Kings and the King of Poisons. During the Bronze Age, arsenic was often included in bronze, which made the alloy harder (so-called "arsenical bronze"). Arsenic was first isolated by Geber (721–815), an Arabian alchemist Albertus Magnus (Albert the Great, 1193–1280) is believed to have been the first European to isolate the element in 1250 by heating soap together with arsenic trisulfide. In 1649, Johann Schröder published two ways of preparing arsenic. Cadet's fuming liquid (impure cacodyl), the first organometallic compound, was synthesized in 1760 by Louis Claude Cadet de Gassicourt by the reaction of potassium acetate with arsenic trioxide. In the Victorian era, "arsenic" (colourless, crystalline, soluble "white arsenic" trioxide) was mixed with vinegar and chalk and eaten by women to improve the complexion of their faces, making their skin paler to show they did not work in the fields. Arsenic was also rubbed into the faces and arms of women to "improve their complexion". The accidental use of arsenic in the adulteration of foodstuffs led to the Bradford sweet poisoning in 1858, which resulted in approximately 20 deaths and 200 people taken ill with arsenic poisoning. Value The base value of each unit of ranges between 1 and 15Ð per unit, with up to 3 units being found at any one time. Presence on Mars: Common Category:Metalloids Category:Chemical elements Category:Arsenic